The recommended level should be in the 35-50% range. If your A/C system is sized properly, you should be able to fall into that level. If your system is oversized, then you may not get below 60% which means your house feels cold and clammy.
If your home has a high humidity level even though you have an A/C system, then you need to get a professional grade dehumidifier. These units can remove over 20 gallons of water in a 24 hour period. Excess humidity is not only bad for your wooden floors and furniture, but it also fosters pests like roaches, dust mites, mold, mildew, etc.
An added benefit from a dehumidifier is the reduced run time of your A/C system. This will reduce your energy consumption and also increase your overall comfort.